Can anyone diagnose this problem?
Yesterday, five of us were shooting near new, well-maintained "Club" AR15s (Bushmaster CMP guns). Using Winchester .223 factory 55gr FMJ. "Q3131" on box. "PMO3" or "PM03" on inside.

All of experienced (multiple times) a) blown primers (at least 10 out of 60 rounds), b) failures to cycle (spent shell ejected, round chambered but trigger not cocked). None of us could get through a 10 round clip.

Is this the ammo or the guns? What to do?
What is the name for this kind of problem? (Besides *&^@#%!!)

These the tighter chambered match guns with non-chrome lined barrel?


What you might be experiencing is a situation where the 5.56 mil-spec loaded ammo is just a little too hot for running in a 223Remington chambered gun.


Ordinarily this will draw out into a big long debate about firing 5.56 in a 223Rem chambered rifle, some are dead set against it while others approach it from the stance of some rifles will tolerate it while others won't.    I'm of the position that 5.56x45mm may be fine in some 223Rem. rifles while others might choke on it, like your CMP/DCM Bushmasters are doing.


I can't help but wonder if maybe there's something going on with the throat of the CMP guns, might the bullet of the Winchester stuff be seating into the lands of the rifling helping to bump pressures a bit?    Probably doubtful if these rifles are chambered for heavier bullets maybe even seated out a bit further for increased case capacity, but one never knows.

I have been shooting that 45gr. winchester [ usa2232 ]  and it is decent. Fired 100rds of lot#12uc50 and 1"groups of 10@100yards. Bought another box of fourty, I had natchez throw a box in with an order and WTF. Lot#ud5139 8, its from the sewer. Crimped in a vegematic and oal lengths differing enough to be caught with the eye.I hope this stuff did not damage my chamber. I really need to find someone to teach me to load my own. I can blast away with store bought federal, thank you federal, and learn to feed my bolt guns properly.
I must reccomend checking the crimp by feel when buying it. If you do not see what I'm talking about, the lot may be good.  

Here are the known bad lots of 1999 Q3131:
PD50, PD90, PF40, PC22, PG62, PF52, PF11, PL31, & PN02.

~ s0ulzer0

IMO - sounds like a .223 SAAMI/5.56 Milspec issue to me.
The Bushmaster DCM Competition Rifle is .223 SAAMI chambered, not 5.56 NATO.

These weren't the "DCM" guns from Bushmaster; just chrome lined, not "match tuned." They are available through some kind of CMP program that provides them to selected State clubs.

Besides, I didn't realize that the actual "DCM" model wasn't chambered for 5.56. I thought you could shoot milspec in any BM rifle??

It's a piece of cake, man.  Go out and buy "The ABC's of Reloading", read it twice, and get yourself a good kit (RCBS Master Reloading Kit).

I was a little nervous getting started at first, but there's nothing to it, as long as you have your head screwed on straight and are able to follow directions.

[:)]

The DCM is what Bushmaster sends out to CMP clubs.
The DCM & the Varmint rifles are the only non-5.56 NATO chambered barreled rifles they make.

The quickest way to know is to read what is stamped on your barrel.

Here's the reply I got from BM:

"The DCM/CMP has a hybrid chambering that uses the tighter SAAMI Spec headspace from the shoulder of the chamber to the bolt face. It has the longer "Leade" or throat that will accommodate the 5.56mm ammunition so it can be used without developing higher pressures as in a .223 caliber chamber."

"Both 5.56mm and .223 caliber ammunition can safely be used in the DCM/CMP rifles."